Sidebar table of contents for "extensions" doesn't show pages

[asmeurer]

For example, at https://data-apis.org/array-api/draft/extensions/fourier_transform_functions.html the sidebar looks like this

It should show the fft and linalg pages under "extensions".

I looked at the rst but I can't tell why this is happening. It doesn't look any different from the API specification pages, which do this correctly.